Cold Iron also has an effect on some magic. Due to its unique crystalline structure, the metal grounds out active spells. This often blunts their power or can nullify a spell entirely. Users of magic will often keep the amount of iron on their person to a minimum in order not to affect their own spell casting.
The Fey will often give iron a wide berth, since they are creatures actually made of magic. Masters of Glamour are capable of creating physical bodies for themselves, and iron is capable of affecting those bodies like a poison. Fey ingesting food cooked or served with iron implements may become sickened. Cuts from iron knives will appear burned along the edges of the wound. A Fey killed by an iron weapon may experience True Death, since the metal could disperse the Fey’s spirit to the point where it is unable to ever successfully reintegrate.